1. Field of the Invention
The present invention relates to an image forming apparatus that prints a document image according to a print instruction and a print controlling method for the same.
2. Description of the Related Art
With promotion of information technology (IT) in offices, interest for security has been rising recently. For example, as seen in repeatedly caused leakage of client information held by companies, confidential information of organizations and privacy of individuals are threatened, which has become a big social issue.
To cope with such an issue, an IT mechanism for providing an access right to electronic confidential information or a monitoring apparatus at firewall is introduced to prevent the confidential information from being leaked to outside of the companies. Alternatively, measures of prohibiting portable media, such as a notebook personal computer (PC) and a universal serial bus (USB) flash memory, from being carried in or out are taken.
By taking the above-described measures using the IT mechanism, the electronic confidential information can be protected to some extent. This is because the electronic information can be referred to only using the IT and it is easier to introduce the IT mechanism thereto.
On the other hand, when confidential information is printed on paper media with an image forming apparatus or the like, carrying out of a sheet having confidential information of organizations or private information of individuals printed thereon can escape the above-described IT mechanism. Accordingly, it is more difficult to confirm and prohibit such a sheet from being carried out than to restrict electronic confidential information from being carried out, which makes it difficult to maintain the security.
To cope with such an issue, various measures for information leakage have been considered. As a first measure for information leakage, a system that embeds tracking information on paper media in addition to a main image using known information embedding techniques, such as the digital watermarking and the 2-dimensional barcode, at the time of printing has been suggested.
Even if information leakage involving paper media occurs, this system can extract the above-described tracking information by analyzing the leaked document. Accordingly, since the responsibility for careless carrying out of a document can be investigated using the tracking information, a deterrent effect can be expected.
Furthermore, as a second measure for information leakage, a system for embedding copy restriction information for prohibiting copying in paper media using known information embedding techniques, such as the digital watermarking and the 2-dimensional barcode, at the time of printing has been suggested.
In this system, a compatible image forming apparatus extracts the above-described copy restriction information to detect whether copying is permitted at the time of execution of a copy operation, thereby being able to control continuance or cancellation of the copy operation for each page.
A system for embedding, as condition information, password information and permitted user information as well as copy restriction information simply indicating whether copying is permitted and for permitting only specific users to copy a document has been suggested. For example, Japanese Patent Laid-Open No. 2003-280469 disclosing a system of this kind is known. Hereinafter, the above-described tracking information and copy restriction information are collectively referred to as “additional security information”.
In the related art, such additional security information can be unconditionally embedded regardless of whether additional security information has previously been embedded in a document.
However, when a plurality of pieces of additional security information is embedded in a document, an image forming apparatus according to the related art may be unable to extract the additional security information due to interference of the plurality of pieces of additional security information.